AbstractBACKGROUNDThis study aims to examine the feasibility of a novel multi‐layer barrier film made entirely from biopolymers, which can be disposed after use in an economically and ecologically acceptable way, by employing mechanical strength and moisture barrier of poly(lactide) (PLA) films and oxygen barrier enhancement of whey protein isolate (WPI) films. The effect of glycerol was also determined. The three‐layer films, PLA/WPI/PLA, were compared with those made of linear low‐density polyethylene films (LLDPE/WPI/LLDPE). Composite structures of three‐layer films obtained by a simple casting method using denatured WPI solution plasticised with glycerol (GLY) at three different ratios of GLY:WPI (1:4, 1:2.5 and 1:1.5). The WPI solution was applied between two base layers of corona‐treated PLA or LLDPE films.RESULTThe multi‐layer films showed good appearance with no noticeably visible change and good adhesion of layers. PLA enhanced tensile strength of the composite structure. Oxygen permeability of the multi‐layer films was significantly lower than the base films. The water vapour permeability of the structure relied mainly on the base films. The plasticiser content did not significantly affect the properties of the multi‐layer structures.CONCLUSIONResults suggested that WPI could work successfully as an alternative oxygen barrier layer of multi‐layer structures. © 2014 Society of Chemical Industry